Smoke-free policies (also referred to as clean indoor air policies) have become an important component of tobacco control across the United States. Previous studies have established that smoke-free policies reduce exposure to secondhand smoke and reduce smoking rates. Smoke-free policies in restaurants and bars may also have unintended beneficial or deleterious consequences on alcohol use and related outcomes because tobacco and alcohol use frequently co-occur, particularly in these settings. The goal of the proposed study is to assess the effects of smoke-free policies in bars and restaurants on alcohol-related car crashes. Nearly three decades of data (1982-2007) will be used to assess the effect of statewide smoke-free restaurant and bar policies on alcohol-related car crash fatalities in the two largest states with smoke-free restaurant and bar policies-California and New York. Taking advantage of two 'natural experiments,'we will address the following questions: 1. In the most populous state in the US, California, did the implementation of smoke-free bars and restaurants increase, decrease, or have no effect on alcohol-related car crashes? 2. Are the effects replicated, a half decade later, in New York--the second most populous state in the US-- that implemented similar bar and restaurant smoke-free policies? A time series quasi-experimental design will be used to assess the effects of smoke-free policies in bars and restaurants on alcohol-related car crashes. California and New York were selected as the study states because they are the largest states with smoke-free laws, and allow for reasonably long follow-ups, maximizing statistical power. We include three levels or types of design comparisons and controls: comparing California with New York, comparing alcohol-related versus non-alcohol-related crash measures, and controlling for trends and patterns in common across all other states. In summary, the proposed study advances the science not only by adding to the meager research to date in this area, but also by using a more powerful design: replication in two populous states, during diverse historical periods, and using data across three decades so we can detect even small effects that nevertheless are substantively important population-wide. PUBLIC HEALTH RELEVANCE: Investigation of the effects of smoke-free laws on alcohol-related car crashes is urgent, as awareness of possible negative or positive side-effects of smoke-free laws may affect the trajectory of dissemination and maintenance of smoke-free laws. If smoke-free laws worsen alcohol-related fatal crashes it would be critical for public health professionals and legislators to act quickly to address this issue, perhaps with measures to reduce crashes while maintaining the health gains from smoke-free policies. If smoke-free laws also reduce alcohol-related crashes, awareness of those side-effects will strengthen support for and implementation of smoke-free policies.